﻿//-----------------------------------------------------------------------
// <copyright file="SingleInstance.cs" company="Microsoft">
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
// <summary>
//     This class checks to make sure that only one instance of 
//     this application is running at a time.
// </summary>
//-----------------------------------------------------------------------

namespace Microsoft.Shell
{
	using System;
	using System.Collections;
	using System.Collections.Generic;
	using System.ComponentModel;
	using System.IO;
	using System.Runtime.InteropServices;
	using System.Runtime.Remoting;
	using System.Runtime.Remoting.Channels;
	using System.Runtime.Remoting.Channels.Ipc;
	using System.Runtime.Serialization.Formatters;
	using System.Security;
	using System.Threading;
	using System.Windows;
	using System.Windows.Threading;

	internal enum WM
	{
		NULL = 0x0000,
		CREATE = 0x0001,
		DESTROY = 0x0002,
		MOVE = 0x0003,
		SIZE = 0x0005,
		ACTIVATE = 0x0006,
		SETFOCUS = 0x0007,
		KILLFOCUS = 0x0008,
		ENABLE = 0x000A,
		SETREDRAW = 0x000B,
		SETTEXT = 0x000C,
		GETTEXT = 0x000D,
		GETTEXTLENGTH = 0x000E,
		PAINT = 0x000F,
		CLOSE = 0x0010,
		QUERYENDSESSION = 0x0011,
		QUIT = 0x0012,
		QUERYOPEN = 0x0013,
		ERASEBKGND = 0x0014,
		SYSCOLORCHANGE = 0x0015,
		SHOWWINDOW = 0x0018,
		ACTIVATEAPP = 0x001C,
		SETCURSOR = 0x0020,
		MOUSEACTIVATE = 0x0021,
		CHILDACTIVATE = 0x0022,
		QUEUESYNC = 0x0023,
		GETMINMAXINFO = 0x0024,

		WINDOWPOSCHANGING = 0x0046,
		WINDOWPOSCHANGED = 0x0047,

		CONTEXTMENU = 0x007B,
		STYLECHANGING = 0x007C,
		STYLECHANGED = 0x007D,
		DISPLAYCHANGE = 0x007E,
		GETICON = 0x007F,
		SETICON = 0x0080,
		NCCREATE = 0x0081,
		NCDESTROY = 0x0082,
		NCCALCSIZE = 0x0083,
		NCHITTEST = 0x0084,
		NCPAINT = 0x0085,
		NCACTIVATE = 0x0086,
		GETDLGCODE = 0x0087,
		SYNCPAINT = 0x0088,
		NCMOUSEMOVE = 0x00A0,
		NCLBUTTONDOWN = 0x00A1,
		NCLBUTTONUP = 0x00A2,
		NCLBUTTONDBLCLK = 0x00A3,
		NCRBUTTONDOWN = 0x00A4,
		NCRBUTTONUP = 0x00A5,
		NCRBUTTONDBLCLK = 0x00A6,
		NCMBUTTONDOWN = 0x00A7,
		NCMBUTTONUP = 0x00A8,
		NCMBUTTONDBLCLK = 0x00A9,

		SYSKEYDOWN = 0x0104,
		SYSKEYUP = 0x0105,
		SYSCHAR = 0x0106,
		SYSDEADCHAR = 0x0107,
		COMMAND = 0x0111,
		SYSCOMMAND = 0x0112,

		MOUSEMOVE = 0x0200,
		LBUTTONDOWN = 0x0201,
		LBUTTONUP = 0x0202,
		LBUTTONDBLCLK = 0x0203,
		RBUTTONDOWN = 0x0204,
		RBUTTONUP = 0x0205,
		RBUTTONDBLCLK = 0x0206,
		MBUTTONDOWN = 0x0207,
		MBUTTONUP = 0x0208,
		MBUTTONDBLCLK = 0x0209,
		MOUSEWHEEL = 0x020A,
		XBUTTONDOWN = 0x020B,
		XBUTTONUP = 0x020C,
		XBUTTONDBLCLK = 0x020D,
		MOUSEHWHEEL = 0x020E,


		CAPTURECHANGED = 0x0215,

		ENTERSIZEMOVE = 0x0231,
		EXITSIZEMOVE = 0x0232,

		IME_SETCONTEXT = 0x0281,
		IME_NOTIFY = 0x0282,
		IME_CONTROL = 0x0283,
		IME_COMPOSITIONFULL = 0x0284,
		IME_SELECT = 0x0285,
		IME_CHAR = 0x0286,
		IME_REQUEST = 0x0288,
		IME_KEYDOWN = 0x0290,
		IME_KEYUP = 0x0291,

		NCMOUSELEAVE = 0x02A2,

		DWMCOMPOSITIONCHANGED = 0x031E,
		DWMNCRENDERINGCHANGED = 0x031F,
		DWMCOLORIZATIONCOLORCHANGED = 0x0320,
		DWMWINDOWMAXIMIZEDCHANGE = 0x0321,

		#region Windows 7
		DWMSENDICONICTHUMBNAIL = 0x0323,
		DWMSENDICONICLIVEPREVIEWBITMAP = 0x0326,
		#endregion

		USER = 0x0400,

		// This is the hard-coded message value used by WinForms for Shell_NotifyIcon.
		// It's relatively safe to reuse.
		TRAYMOUSEMESSAGE = 0x800, //WM_USER + 1024
		APP = 0x8000,
	}

	[SuppressUnmanagedCodeSecurity]
	internal static class NativeMethods
	{
		/// <summary>
		/// Delegate declaration that matches WndProc signatures.
		/// </summary>
		public delegate IntPtr MessageHandler(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled);

		[DllImport("shell32.dll", EntryPoint = "CommandLineToArgvW", CharSet = CharSet.Unicode)]
		private static extern IntPtr _CommandLineToArgvW([MarshalAs(UnmanagedType.LPWStr)] string cmdLine, out int numArgs);


		[DllImport("kernel32.dll", EntryPoint = "LocalFree", SetLastError = true)]
		private static extern IntPtr _LocalFree(IntPtr hMem);


		public static string[] CommandLineToArgvW(string cmdLine)
		{
			IntPtr argv = IntPtr.Zero;
			try
			{
				int numArgs = 0;

				argv = _CommandLineToArgvW(cmdLine, out numArgs);
				if (argv == IntPtr.Zero)
				{
					throw new Win32Exception();
				}
				var result = new string[numArgs];

				for (int i = 0; i < numArgs; i++)
				{
					IntPtr currArg = Marshal.ReadIntPtr(argv, i * Marshal.SizeOf(typeof(IntPtr)));
					result[i] = Marshal.PtrToStringUni(currArg);
				}

				return result;
			}
			finally
			{

				IntPtr p = _LocalFree(argv);
				// Otherwise LocalFree failed.
				// Assert.AreEqual(IntPtr.Zero, p);
			}
		}
	}

	public interface ISingleInstanceApp
	{
		bool SignalExternalCommandLineArgs(IList<string> args);
	}

	/// <summary>
	/// This class checks to make sure that only one instance of 
	/// this application is running at a time.
	/// </summary>
	/// <remarks>
	/// Note: this class should be used with some caution, because it does no
	/// security checking. For example, if one instance of an app that uses this class
	/// is running as Administrator, any other instance, even if it is not
	/// running as Administrator, can activate it with command line arguments.
	/// For most apps, this will not be much of an issue.
	/// </remarks>
	public static class SingleInstance<TApplication>
				where TApplication : Application, ISingleInstanceApp
	{
		#region Private Fields

		/// <summary>
		/// String delimiter used in channel names.
		/// </summary>
		private const string Delimiter = ":";

		/// <summary>
		/// Suffix to the channel name.
		/// </summary>
		private const string ChannelNameSuffix = "SingeInstanceIPCChannel";

		/// <summary>
		/// Remote service name.
		/// </summary>
		private const string RemoteServiceName = "SingleInstanceApplicationService";

		/// <summary>
		/// IPC protocol used (string).
		/// </summary>
		private const string IpcProtocol = "ipc://";

		/// <summary>
		/// Application mutex.
		/// </summary>
		private static Mutex singleInstanceMutex;

		/// <summary>
		/// IPC channel for communications.
		/// </summary>
		private static IpcServerChannel channel;

		/// <summary>
		/// List of command line arguments for the application.
		/// </summary>
		private static IList<string> commandLineArgs;

		#endregion

		#region Public Properties

		/// <summary>
		/// Gets list of command line arguments for the application.
		/// </summary>
		public static IList<string> CommandLineArgs
		{
			get { return commandLineArgs; }
		}

		#endregion

		#region Public Methods

		/// <summary>
		/// Checks if the instance of the application attempting to start is the first instance. 
		/// If not, activates the first instance.
		/// </summary>
		/// <returns>True if this is the first instance of the application.</returns>
		public static bool InitializeAsFirstInstance(string uniqueName)
		{
			try
			{
				commandLineArgs = GetCommandLineArgs(uniqueName);

				// Build unique application Id and the IPC channel name.
				string applicationIdentifier = uniqueName + Environment.UserName;

				string channelName = String.Concat(applicationIdentifier, Delimiter, ChannelNameSuffix);

				// Create mutex based on unique application Id to check if this is the first instance of the application. 
				bool firstInstance;
				singleInstanceMutex = new Mutex(true, applicationIdentifier, out firstInstance);
				if (firstInstance)
				{
					CreateRemoteService(channelName);
				}
				else
				{
					SignalFirstInstance(channelName, commandLineArgs);
				}

				return firstInstance;
			}
			catch
			{
				// Most likely caused by duplicate process which is shutting down;
				// signalling closing process will throw an exception. In this case
				// simply allow the new process to open.
				return true;
			}
		}

		/// <summary>
		/// Cleans up single-instance code, clearing shared resources, mutexes, etc.
		/// </summary>
		public static void Cleanup()
		{
			if (singleInstanceMutex != null)
			{
				singleInstanceMutex.Close();
				singleInstanceMutex = null;
			}

			if (channel != null)
			{
				ChannelServices.UnregisterChannel(channel);
				channel = null;
			}
		}

		#endregion

		#region Private Methods

		/// <summary>
		/// Gets command line args - for ClickOnce deployed applications, command line args may not be passed directly, they have to be retrieved.
		/// </summary>
		/// <returns>List of command line arg strings.</returns>
		private static IList<string> GetCommandLineArgs(string uniqueApplicationName)
		{
			string[] args = null;
			if (AppDomain.CurrentDomain.ActivationContext == null)
			{
				// The application was not clickonce deployed, get args from standard API's
				args = Environment.GetCommandLineArgs();
			}
			else
			{
				// The application was clickonce deployed
				// Clickonce deployed apps cannot recieve traditional commandline arguments
				// As a workaround commandline arguments can be written to a shared location before 
				// the app is launched and the app can obtain its commandline arguments from the 
				// shared location               
				string appFolderPath = Path.Combine(
					Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), uniqueApplicationName);

				string cmdLinePath = Path.Combine(appFolderPath, "cmdline.txt");
				if (File.Exists(cmdLinePath))
				{
					try
					{
						using (TextReader reader = new StreamReader(cmdLinePath, System.Text.Encoding.Unicode))
						{
							args = NativeMethods.CommandLineToArgvW(reader.ReadToEnd());
						}

						File.Delete(cmdLinePath);
					}
					catch (IOException)
					{
					}
				}
			}

			if (args == null)
			{
				args = new string[] { };
			}

			return new List<string>(args);
		}

		/// <summary>
		/// Creates a remote service for communication.
		/// </summary>
		/// <param name="channelName">Application's IPC channel name.</param>
		private static void CreateRemoteService(string channelName)
		{
			BinaryServerFormatterSinkProvider serverProvider = new BinaryServerFormatterSinkProvider();
			serverProvider.TypeFilterLevel = TypeFilterLevel.Full;
			IDictionary props = new Dictionary<string, string>();

			props["name"] = channelName;
			props["portName"] = channelName;
			props["exclusiveAddressUse"] = "False";

			// Create the IPC Server channel with the channel properties
			channel = new IpcServerChannel(props, serverProvider);

			// Register the channel with the channel services
			ChannelServices.RegisterChannel(channel, true);

			// Expose the remote service with the REMOTE_SERVICE_NAME
			IPCRemoteService remoteService = new IPCRemoteService();
			RemotingServices.Marshal(remoteService, RemoteServiceName);
		}

		/// <summary>
		/// Creates a client channel and obtains a reference to the remoting service exposed by the server - 
		/// in this case, the remoting service exposed by the first instance. Calls a function of the remoting service 
		/// class to pass on command line arguments from the second instance to the first and cause it to activate itself.
		/// </summary>
		/// <param name="channelName">Application's IPC channel name.</param>
		/// <param name="args">
		/// Command line arguments for the second instance, passed to the first instance to take appropriate action.
		/// </param>
		private static void SignalFirstInstance(string channelName, IList<string> args)
		{
			IpcClientChannel secondInstanceChannel = new IpcClientChannel();
			ChannelServices.RegisterChannel(secondInstanceChannel, true);

			string remotingServiceUrl = IpcProtocol + channelName + "/" + RemoteServiceName;

			// Obtain a reference to the remoting service exposed by the server i.e the first instance of the application
			IPCRemoteService firstInstanceRemoteServiceReference = (IPCRemoteService)RemotingServices.Connect(typeof(IPCRemoteService), remotingServiceUrl);

			// Check that the remote service exists, in some cases the first instance may not yet have created one, in which case
			// the second instance should just exit
			if (firstInstanceRemoteServiceReference != null)
			{
				// Invoke a method of the remote service exposed by the first instance passing on the command line
				// arguments and causing the first instance to activate itself
				firstInstanceRemoteServiceReference.InvokeFirstInstance(args);
			}
		}

		/// <summary>
		/// Callback for activating first instance of the application.
		/// </summary>
		/// <param name="arg">Callback argument.</param>
		/// <returns>Always null.</returns>
		private static object ActivateFirstInstanceCallback(object arg)
		{
			// Get command line args to be passed to first instance
			IList<string> args = arg as IList<string>;
			ActivateFirstInstance(args);
			return null;
		}

		/// <summary>
		/// Activates the first instance of the application with arguments from a second instance.
		/// </summary>
		/// <param name="args">List of arguments to supply the first instance of the application.</param>
		private static void ActivateFirstInstance(IList<string> args)
		{
			// Set main window state and process command line args
			if (Application.Current == null)
			{
				return;
			}

			((TApplication)Application.Current).SignalExternalCommandLineArgs(args);
		}

		#endregion

		#region Private Classes

		/// <summary>
		/// Remoting service class which is exposed by the server i.e the first instance and called by the second instance
		/// to pass on the command line arguments to the first instance and cause it to activate itself.
		/// </summary>
		private class IPCRemoteService : MarshalByRefObject
		{
			/// <summary>
			/// Activates the first instance of the application.
			/// </summary>
			/// <param name="args">List of arguments to pass to the first instance.</param>
			public void InvokeFirstInstance(IList<string> args)
			{
				if (Application.Current != null)
				{
					// Do an asynchronous call to ActivateFirstInstance function
					Application.Current.Dispatcher.BeginInvoke(
						DispatcherPriority.Normal, new DispatcherOperationCallback(SingleInstance<TApplication>.ActivateFirstInstanceCallback), args);
				}
			}

			/// <summary>
			/// Remoting Object's ease expires after every 5 minutes by default. We need to override the InitializeLifetimeService class
			/// to ensure that lease never expires.
			/// </summary>
			/// <returns>Always null.</returns>
			public override object InitializeLifetimeService()
			{
				return null;
			}
		}

		#endregion
	}
}
